This research investigates the relationship between family function, subjectively experienced economic security, and childhood reactivity, three possible mediators of the well-documented gradient in mental and physical health outcomes according to socioeconomic status. Sympathetic, parasympathetic, and adrenocortical reactivity will be measured in children, within families homes, during a standardized protocol involving mild cognitive and physical challenges. Physiological responses will be related to: (1) the frequency of a set of daily routines that focus on child-caretaker interaction; (2) the stability of children's and parents daily schedules; (3) physiological markers of chronic stress in children; (4) parents self-rated subscription to and difficulty in achieving community standards of economic security; and (4) child functional outcomes, including problem behaviors linked to psychiatric risk (internalizing, externalizing), educational performance, and respiratory symptoms. It is hypothesized that ecologic stress (low stability, infrequent routines, high chronic stress) predicts high reactivity. However, high reactivity has also been proposed as an index of sensitivity to ecologic stress. It is therefore hypothesized that a highly vulnerable group of children can be identified, clustered in but not limited to lower SES, who show high reactivity in the context of ecologic stress and high parental economic insecurity. It is further hypothesized that these children will have comparatively high prevalence of problem behaviors, poor academic performance, and frequent respiratory symptoms.